The invention relates to devices for mounting electrical components on circuit boards and, more especially, to a method and means for removing components which are attached to feed tapes by their leads by shearing portions of the tips of the leads, centering the component bodies upon a longitudinal axis generally midway between the feed tapes, forming the leads for insertion into spaced holes of the circuit board, and inserting the leads into these holes.
Printed circuit boards are formed with appropriately spaced lead receiving holes to provide for mounting of the components to the circuit board by insertion of the component leads through the holes and clinching the leads to the underside of the circuit board. Machines for mounting the components in this manner are disclosed in U.S. Pat. No. Re. 27,968 and U.S. Pat. No. 3,593,404, cross-referenced above, are typical of the prior art. Such machines receive components of various sizes and shapes which are mounted onto the tapes by their oppositely extending leads. As may be appreciated, the tolerances for insertion of the leads into the small, spaced holes of the circuit board are critical, and a component body which is off-center relative to the longitudinal axis between the spaced tapes may not allow a proper mounting of the component onto the board. For instance, the components, during mounting upon the spaced tapes, are oftentimes off-center by as much as 0.030 inches due to the tolerances of the machine which mounts the components onto the tape. This amount of miss-centering may cause misinsertion of a lead into a hole and bending of the lead and mismounting of the component. Further, in order to more closely populate components onto a circuit board, it is desirable to form or bend the leads as closely as possible to the component body. If the component arrives at the lead formers in such an off-center condition, then at least one of the leads will be formed or bent 0.030 inches from the body and require mounting holes which are spaced further apart than ideal for maximum population of the board.
In order to overcome this particular problem, a method and apparatus of centering the component bodies prior to lead forming was devised and is disclosed in the above cross-referenced U.S. Application Ser. No. 319,405 now U.S. Pat. No. 4,417,683. Although very efficiently functional in most situations, problems have occurred with this machine when component leads of very thin cross section must be handled. For instance, this prior art device engages the body of the component for centering it upon a longitudinal axis between the feed tapes prior to removing the components from the tapes by cutting the end portions of the leads, such that the leads of an off-center component are moved in a direction normal to the length of the tapes and one lead will be pulled from a tape while the oppositely extending lead will be pushed into or through the other tape. With very fragile leads, there may be damage to the muniscus or point of connection between the component and the lead which is being pulled from a tape and the oppositely extending lead may bend during pushing of it toward the other tape, such that the lead formers may not straighten the lead properly prior to insertion and mismounting of the component onto the circuit board will occur, or a defective component will be mounted upon the circuit board due to the damage to the connection between a lead and body.
The present invention overcomes this difficulty in handling components with fragile leads by trimming the ends of the leads to remove the components from the tapes prior to centering of the components about the longitudinal axis between the tapes for subsequent forming and inserting of the leads into the holes of the circuit board.
The above-referenced U.S. Pat. No. 2,856,998 discloses a device for centering electrical components. However, the device of this patent does not handle components which are fed on tapes, and it does not trim the ends of the leads prior to centering the components.
The above-referenced U.S. Pat. No. 3,078,466 discloses a device for mounting electrical components onto circuit boards in which the mounting device has two variably spaced portions which are varied in spacing each cycle for various body lengths. However, the variation of the spacing is in incremental steps of 0.1 inches or the like and is stated to be for bodies of considerably different lengths. This device does not handle components which are taped, nor does it cut the leads of the components prior to insertion or address the problem of centering the component bodies.
U.S. Pat. No. 3,594,889 discloses a machine having yieldable inside formers such that component leads of various diameters may be handled during forming of the leads. This device also does not address the problem of handling components whose bodies are off-center when received by the lead formers.
The only prior art of which applicant is aware which addresses the problem of forming or bending the leads as closely to the body as possible in order to increase population of the components onto a circuit board and of centering the bodies relative to a longitudinal axis such that the leads are uniformly bent closely to the body of the component is the above-referenced U.S. Pat. Application Ser. No. 319,405 which, as indicated above, cannot efficiently and reliably mount components whose leads are too fragile.
Accordingly, it is an object of this invention to improve upon the prior art method and apparatus of centering bodies of various lengths of components which are sequenced and attached by their leads to sequencing tapes, such that the leads of the components may be formed or bent as close as possible to the bodies of the components for increased population of the components onto the circuit board. By the method and apparatus of the instant invention, the components are removed from the tapes prior to centering so that components having very fragile leads will not be damaged at the connection between a lead and body of the component and leads will not be bent, as will occur when centering of the bodies of such components is accomplished while the components are still attached to the sequencing tapes.